Monomethine dyes containing a thiobarbituric acid nucleus



United States Patent MONOMETIHNE DYES CONTAINING A TI-IIOBARBITURIC ACID NUCLEUS Grafton H. Keyes, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application November 14, 1951, Serial No. 256,383

7 Claims. (Cl. 260-2404) This invention relates to new monomethine dyes containing a pyrrole nucleus and a thiobarbituric acid nucleus and a method for making such dyes.

The new dyes of my invention can be represented by the following general formula:

wherein R, R1, and R2 represents an alkyl group, such as methyl, ethyl, n-propyl, n-butyl, n-amyl, n-heptyl, n-decyl, n-dodecyl (lauryl), cyclohexyl, benzyl (phenylmethyl),

etc., (especially a primary alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from- 1 to 4) or an aryl group, such as phenyl, 0-, m-, and p-tolyl, etc., (especially a mononuclear aryl group of the benzene series), and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus of the pyrrole series.

The monomethine dyes represented by Formula I above can be used to prepare filter layers and backing layers for photographic plates and film, and are characterized by high absorption properties and good bleachability by photographic processing bleaching baths. Dyes similar to those of Formula I, but wherein both nitrogen atoms of the barbituric acid nucleus are unsubstituted are not readily dispersible and hence frequently cause difliculty in the preparation of filter layers, while the corresponding disubstituted derivatives do not have suificient affinity for the silver ion to be of practical use. The preparation of filter layers comprising the dyes of Formula I is described in Herz and Keyes U. S. application Serial No. 50

256,240, filed on even date herewith, now U. S. Patent 2,719,088, issued September 27, 1955.

The dyes represented by Formula I can advantageously be prepared by condensing an aldehyde selected from those represented bythe following general formula:

II. /Z\ 0 wherein R, R1, and Z have the values set forth above,

with a thiobarbituric acid selected from those represented by the following general formula:

III.

wherein R2 has the values given above.

2,739,147 Patented Mar. 20, 1956 condensed rings, such as the indole nucleus, the pyrrocoline nucleus, 'etc.

The condensations can be accelerated by heat and can be performed most advantageously by heating the reactants under reflux in an alcohol solution. The dyes i can be separated from the reaction mixtures by chilling.

They can then be recrystallized, if desired.

The following examples will serve to illustrate more fully the manner whereby I practice my invention.

l-phenyl-2-thiobarbituric acid (2.1 g., 1 mol.), 2,5- dimethyl-1-phenylpyrrole-3-aldehyde (2 g., 1 mol.) and absolute ethyl alcohol (50 ml.) were refluxed for 15 minutes. Dye separated on chilling. The yield of crude 5 well washed dye was 90% of theory. The dye was puzrified by dissolving in boiling pyridine, filtering while hot and then adding about 3 volumes of methyl alcohol and chilling. After two such treatments, a 60% yield of dye was obtained as brownish-yellow crystals, M. P. 247-250 0. with decomposition.

. Anal. calcd. for CzsHwNsOzS: C, 68.80; H, 4.77.

FQ1111d,C, 69.2; H, 5.0.

l-phenyl-Z-thiobarbituric acid has been described by T. Pavolini and F. Gambarin, Anal. chim. Acta., 3, 29 1949 Example 2.5-[(1-cyc[0hexyl-2,5-dimethyl-3-pyrryl) methylenel-l-phenyl-2-thi0barbituric acid A mixture of 2.1 g. (1 mol.) of 1-phenyl-2-thiobarbituric acid, 2.05 g. (1 mol.) of l-cyclohexyl-2,5-dimethylpyrrole-3-aldehyde and ml. of absolute ethyl alcohol were heated under reflux for a 15-minute period. The yield of crude washed dye obtained was 83% of theory. After two recrystallizations the dye was obtained as brownish-yellow crystals, M. P. 270-272 C. dec.

' Example 3.5-[(2,5 dimethyl-1-n-propyl-3-pyrryl) methylene]-1-phenyl-2-thiobarbituric acid alcohol were refluxed together for 15 minutes. Yield of crude washed dye was 40% and after two recrystalliza- The value for Z includes not only the simple pyrrole nucleus, but also tions the dye was obtained as brownish-yellow crystals, M. P. 282-284 C. dec. 7

Example 4.- 5 [(1-lauryl 2,5-dimethyl-3-pyrryl) methylenel-l--phenyl-2-thiobarbituric acid Example 5 .-5 (2,5 -dimethyl-1 -phenyl-3-pyrryl methylenel-I-ethyl-2-thi0barbituric acid liq A mixtureof 1.7 g. @(1 mol.) of .leethyl-2-thiobarbituric acid, 2 g. (1mol.) of 2,5-dimethyl-1-phenylpyrrole-S-aldehyde and 50ml. of absolute ethyl alcohol were heated together under reflux-tor 15 minutes. The yield of well washed dye was 86% .of'thcory. .Aftentwo recrystallizations the .dye was obtained .as brownishyellow crystals in 64% Yield, M. P. 246248 C. dec.

The 1-ethyl-2-thiobarbituric acid used in above example was'prepared as follows:

18.4 g. (1 mol.+l00% excess) of so'dium-was dissolved in 300 ml..of absolute ethyl alcohol; after cooling this solution to about 60, 128 g. (1 mol.+l00% excess) of ethyl malonate wasadded with mechanical stirring, followed by "41.6 g. (1 mol.) of ethyl-thiourea. The reaction mixture was heated at..steam-bath.temperature with stirring for a 6-hour period and without stirring for a further 72 hours. 300 ml. of cold water was then added to the mixture and most 'of"-the alcohol was removed by distillation. The residue was treated withl liter'of cold water and. theimixture. filtered. This filtrate was then acidified. Theproduct'which separated was collected on filter, washed well with water and dried. "It

was used without further purification. 'The'yield'was. D

89% or theory.

Example 6.---[ (I benzyl-ZjS-dimethyl fi pyrryl) methylene]1=ethyl-Zahiobarbituria.acid

A mixture of 1.7 g. (1 mol.) of 1-ethyl-2-thiobarbit-uriczacid, 2.155;. (1 mol.) of lebengylirdimethylpyr-role-3-aldehyde .and '50 ml..of absolutecthyhalcohol was trefluxed togetherforlS minutes. Dyerscpasated from. the hot. reaction -mixture. The yieldegf crude washed dye obtained was.85% qof. theory. Alter twov recrystalliaations .a. 62% vyield of. dye.- as ,-yellow crystals M. P. 252-254 'C. dec. was obtained.

4 Example 7 .--5 -[(1 ,2-dimethyl-3-ind0lyl methylene]- 1 -ethyl-2-thiobarbituric acid On refluxing a mixture of I-ethyl-Z-thiobarbituric.acid (1.7 g., 1 mol.) and 1,2-dimethyl-3-indolealdehyde (1.7 g., 1 mol;) and absolute ethyl alcohol (50 ml.) for a 15-minute period, dye-separated from the hot reaction mixture. The yield of crude swashed'dye-was 82% of theory. It was obtained as brownish crystals, M. P. 246-248 C. dec. after two recrystallizations.

Other dyes which can 'be prepared according'tothe above general method include those illustrated in the following examples.

Example 8.5-[(4-carbethoxy.-3,5-dime;hyle2 pyrryl) methylene]-1-ethyl-2-thi0barbituric acid .A-mixture of ;1.7 g. (1 mol.) of .1-ethyl:2e,thiob.arbituricacid, 1.95 g. (1 mol.) of 4-carbethoxy-,3.5-.dimethylpyrrole-Laldehyde [Stern &',Klebs--.-Ann. 500, 9,1 (19.3.2)]an'd 50 ml. of abso1ute ethyl alcohol were refluxed for 15 minutes. A 91% yield. of crude, washed dye was obtained. After two recrystallizationsit was obtained as yellowcrystals, M. P. 273-275 .C. dec.

Example 9.-5'-[(2,5-dimethyl-1-phenyl3-pyrryl) methylene]-2-thi0barbituric acid bleached by photographic developers.

Example 10.5- (1-n-heptyl-2,5-dimethyl-3-pyrryl) methylene] -2'-thiobarbituric acid 1.45 g. (1 mol.) of thiobarbituric acid, 2.2 g. (1 mol.) of 1-n-heptyl-2,5-dimethylpyrrole-3-aldehyde and 50 cc.

.of absolute ethyl alcohol were refluxed together for a periodof fifteen minutes. Dye separated on. chilling. The yield oicrudecwashed dye was 60 per cent of theoretical.

After two recrystallizations from a mixture of pyridine and methyl alcohol, it was obtained as greenish yellow Example 11. 1,3 dietliyl 5 2,5 dimethyl 1 phenyl-3-pyrryl) methylene] -2-thiobarbituric acid (I323: il s HCCOH=C o=s m -CH; CN $.11. I

,2 g. (1 mol) of 1,3-diethyl-2-thiobarbituric acid, 2 g. (1 mol) of 2,5-dimethyl-1-phenylpyrrole-3-aldehyde and 50 cc. of absolute ethyl alcohol were refluxed together for a period of fifteen minutes. Dye separated on chilling. An 87 per cent yield of well-washed crude dye was obtained. After repeated recrystallizations from a mixture ofpyridine and methyl alcohol, the dye was obtained as orange-yellow crystals, M. P. 177-179 C. This dye gives a yellow alcohol solution which is bleached by photographic developers.

Example 12.5[(2,5-dimethyl-1-phenyl-3-pyrryl)methylene] barbituric acid 1.3 g. (1 mol) of barbituric acid, 2 g. (1 mol) of 2,5- dimethyl-1-phenylpyrrole-3-aldehyde and 50 cc. of absm lute ethyl alcohol were refluxed together for a period of fifteen minutes. Dye separated on chilling. The yield of well-washed crude dye was 97 per cent of theoretical. After two recrystallizations from a pyridine-methyl alcohol mixture, the dye was obtained as yellow crystals, M. P. 246-249 C. This dye gives a yellow alcoholic solution which is bleached by photographic developers.

The intermediates represented by Formula II above can be prepared by condensing a compound selected from those represented by the following general formula:

IV. /Z\- ri-o=bn 1'. l. wherein R, R1, and Z have the values set forth above with formamide in the presence of phosphorusoxyehloride. See Nenitzeseu et al.--Bull. Soc. Chim. Romania 11, 135 (1929), and Brooker & SpragueJour. Am. Chem. Soc. 67, 1869 (1945). The pyrrole bases of Formula IV can be prepared according to the process of Lions et al., Proc. Royal Soc. New South Wales, 71, 92 (1937). For a general outline of these methods see Brooker et 2.1. U. S. Patent 2,268,798, issued January 6, 1942; Brooker et a1. U. S. Patent 2,298,731, issued October 13, 1942; Brooker et a1. 2,409,612, issued October 22, 1946; and Sprague et a1. U. S. Patent 2,515,905, July 18, 1950.

The intermediates represented by Formula III above can be prepared by condensing a compound selected from those represented by thefollowing general formula Rz-N-E-NH: wherein R2 has the values set forth above, with a dialkyl malonate, e. g., diethyl malonate, in the presence of an alkali metal alcoholate, e. g., sodium ethylate. Such a method is described in Example 5 above.

In the above examples the crude dyes were collected on a filter after chilling the reaction mixtures, and the crude dyes were washed with methyl alcohol in each instance. The crude washed dyes were recrystallized by dissolving in pyridine (boiling) and precipitating the chilled solution with methyl alcohol.

A number of the intermediates included within the scope of Formula II above have been previously described in'U. S. Patent 2,515,912, issued July 18, 1950, to Van Lare and Brookerj What I claim as my invention and desire secured by Letters Patent of the United States is:

1. A monomethine dye selected from those represented by the following general formula:

wherein R and R2 each represents an aryl group of the benzene series, R1 represents a primary alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from 1 to 4, Z represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the pyrrole series.

3. The monomethine dye represented by the following formula:

0 CaHs HC-C-CH=C H C --CH3 C-N h l I 4. A monomethine dye selected from those represented by the following general formula:

wherein R represents an aryl group of the benzene series, R1 and R2 each represents primary alkyl group of the formula CnH2n+1 wherein n represents a positive integer of from 1 to 4, and Z represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the pyrrole series.

5. The monomethine dye represented by the following formula:

0 0,13 1. gnonornethine dye represented by the following {L 1 ennyl H0-- o-,0H=C c=s 0 10 H;GY-e l'L-CH; G t-1? 5 /)-N H HC.C-CH=C 0=.s 5.11 H|C 91-0118 \CN/ 6. A monomethine dyeselected from-those represented l by the following general formula: 10 (lhHm) 0 III: ,Z il-N References Cited in the file of this patent ?t =b-on=,c o- -s UNITED STATES PATENTS R 2,170,805 Brooker Aug. 29, 1939 A H 2,185,182 Block r an- 2., 1940 wherein R and R1 each represents a primary alkyl group 12365907 Ke'ndau 911941 of the formula cnH2n+1 wherein n represents a positive 2,548,571 a P 19-511 integer of from 1 to '4, R2 represents anharyl group of 20 FOREIGN PATENTS the benzene series, and ,Z represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the pyrrole 529,440 ,Great Britain 1940- series. $162,757 Great Britain July 14, 1944 

1. A MONOMETHINE DYE SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 